Compound for mixing with cements and method of making the same



p.;t...*..a N... 11.1936

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COMPOSITlONS, COATING 0R PLASTIC.

UNITED STATES PATENT OFFICE RICHARD BUHMAN, OF CASPER, WYOMING COMPOUND FOR MIXING WITH. CEMENTS AND METHOD OF MAKING THE SAME No Drawing.

The present invention relates to a process of cementin wells and a composition of matter We cement which is used for the foregoing or similar purposes where 6 it is desired to retard the initial set of the cement and at the same time hasten the final set of the cement.

In the drilling of oil wells it sometimes happens that a stratum of water bearing sand 10 is encountered before the stratum of oil bearing sand is reached, and it then becomes necessary to cement the well and seal ofl:' the water bearing sand so that the water will not leak into the well and interfere with obtaining the oil from the underlying stratum of oil bearing sand.

This is ordinarily accomplished by pumping a mixture of cement and water, termed cement slurry, down through the casing and 2 causing it to pass around the lower edge of the casing and rise into the space between the exterior of the casing and the walls of the hole. After the cement slurr has thus been forcibly pumped Tim and the job is completed, it would ordinarily require a considerable eriod of time, as from eight to fourteen ays, for the cement to set and harden. Drilling cannot be resumed until the cement has hardened, and obviously it is an advantage to accelerate the hardening of the cement in order to reduce the loss of time and cut down the delay before drilling can be continued.

This desired acceleration of the hardening of the cement can be accomplished by adding certain chemicals to the cement and, of those that have been used up to the present time calcium chloride seems to be the most popular.

e 1 cu y with all of the accelerators that have been used, and especially with calcium chloride, is that they begin to work as soon as the cement is mixed with water, and as the operation of cementing a well requires from one to three hours, durin which time the cement slurry must be uid enough to be pumped, it may easily, and frequently does happen, that the cement begins to set and harden in the casing and even in the pump before the job is completed. One way to avoid 5 this is to make the slurry so thin that the Application filed April 5, 1924. Serial No. 704,318.

initial set is delayed long enough to complete the operation, although this is a serious drawback, as the excess of water must either settle out or be absorbed by the calcium chloride if any acceleration of the hardening is to be accomplished. Furthermore, any excess of water makes the slurry so thin that the cement settles out very rapidly where it is not desired to settle out, and the portion that has thus settled being without excess water sets very rapidly due to the dehydrating action of calcium chloride. This is frequently the cause of the cement hardening in the pump and casing before the job is completed. Thus if the cement slurry containing calcium chloride is thin enough for safe operation, the cement tends to settle out, and the settled out portion hardens very rapidly. But it is very doubtful if enough settling occurs in the hole to be of benefit, if there is a column of 500 feet or more, and thisis being agitated until the job is completed. If the job requires from one to two hours for completion, the cement will begin to set soon after, although slowly with the excess of water present, but fast enough to largely prevent this excess of water from separating out on top. In this way the purpose of the calcium chloride is partly defeated, as it has first to absorb the excess of water that its very introduction made necessary.

According to the present invention this difliculty is solved by providing for etarding the initial set of the cement so that tlTF is ample time or get ingmment in position and finishing the job before the cement starts to harden, and at the same time hastening or ccelerating the finalset of the cement, so that t e135? of time Bertie drilling can be resumed will be reduced to a minimum.

With the foregoing throughts in mind it will be understood that the present invention comprises a process of cementing wells, and also a compound for mixing with cements, whereby the initial set is delayed and the final set accelerated, and the necessity of using an excessive quantity of water in the mixing of a cement slurry avoided.

In forming the slurry cement is ordinarily mixed with about bv weight of water in order to give a slurry a iquid 100 magnifier the setting sometimes begins before and later hasten in g theh aii 3o enough to be pumped. Obviously, the time the initial setis retarded, can be conamount of water used is important, since too trolled to suit the requirements. much will delay the setting of the cement, According to the foregoing reaction caland too little will make the pumping difficult. cium chloride is slowly formed in the cement, The operation of pumping the cement slurry and as this crystallizes with a relatively large in forcing it into position in the space suramount of water, it act-s as a dehydrating rounding the casing ordinarily requires from agent and hastens the final set or hardening one to three hours and sometimes even longer, of the cement. It has been found in actual depending upon conditions, and, of course, practice that the addition of iron chl ide premature setting of the cement would be to the gauging water of the cm fatal to the job. WVhere calcium chloride without the additlcifibf lziiim chloride alone is used with the cemen oaccee e acts in the dearest-ma i first retarding s W i s. remas the' is completed, with the result that ment. Both of these qualiti are highly dethe cement may harden in the casing or in the sirable in the cementing of oil wells and other pump. When this happens it is usually necanalogous operations, because it allows, in essary to stop operations, drill the cement the first place, more time for placing the ceout of the casing and start all over again. ment and in the second place, there is less According to the present invention a redelay before drilling can be resumed. The agent is added to the cement which serves formation of iron h droxide in the cement to delay the initial set and a lerate the final acts as an interna iibricant and makes a handeningoithewt, This reagent a so more uniform "arid c'reamy slurry. The iron allows the use of a smaller quantity of water hydroxide also tends to prevent the segregain the slurry and tends to prevent the settling tion of finer and coarser particles of the ceout of the cement from the slurry. It will ment and the settling out of the cement from thus be seen that the addition of this single thewater. It also makes thecement easier and reagent will overcome all of the difficulty safer to pump, with less tendenc to clog the caused by the addition of calcium chloride to valves, and after the cement has ally hardthe cement for the purpose of causing an ened it is tough and thoroughly water-proof early hardening thereof. This reagent may and will not crack under the pounding action o rmaylgiotbensedjn combination with calof the drills. cium ciloride, and it will improve the qual- It has been found that iron andaluminum ity of the cement by making it tougher and, salts act similarly and aluminum chloride therefore, less liable to crack when subjected can be used instead of the ferric chloride to the pounding of the drill. with substantially the same results. In fact, This reagent, which may or may not be any soluble metallic salt can be used which used in s: cium c on e, 15 of such a character as to form an insoluble comprises a a inu metallic hydroxide in reaction with the ce- These salts are 1e gauging wa er ment. I do not wish to restrict myself to the used in making the cement slurry, and must use of either ferric chloride or 1 'num be such that the corresponding calcium salts chloride or to any particular metallic salt, which are automatically formed in the ceslnce any metallic salt which is soluble and ment on the addition of the water thereto will react with the cement in the same mancrystallize with relatively large amounts of ner as the ferric chloride to produce mewater, such as chlorides, nitrates and sultallic hydroxide and bring about a slow formation of calcium chloride can be used. These salts can be used either sin ularl or in mixture with each other, and they can be usgd either with or without calcium chlor1 e. .7

In ractice it has been found that 1.520 of OOEIIDBIClal fgalciumnchlnride wi of commercial grricichloride by wei lit 1n terms of ggne t gives good res n ta ntthough fiiifi' certain conditions it may be desirable to use up to 3% or even more of both the metallic salt and calcium chloride. The quantity to be used is necessarily subject to variation to suit different conditions. The ferric chloride or other metallic salt can be used without the calcium chloride if desired, although it has been found advantageous to use a mixture of calcium chloride and ferric chloride, since the calcium chloride is cheaper and more effective in accele oregoing result is accomplished in the following manner. When cement is mixed with water, calcium hydroxide is set free. If the water We iron salt, a reaction takes place by which the insoluble iron hydroxide and a soluble calcium salt are produced, according to the o owing reaction:

By the format-ion of iron hydroxide in the cement during and after the mixing with water, and the resulting intimate and uni form distribution of the iron hydroxide, sulficient moisture is retained uniformly throughout the cement to retard the initial set of the cement, even in the presence of drying agents, such as calcium chloride. By varying the amount of the iron salt used, the length of I06. COMPOSITIONS,

COATING OR PLASTIC.

crating the final hardening, while the ferric chlorides operate to retard the initial set.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is,

The method of preparing a cement for use in cementing oil oil wells or the like, which comprises first making a cement of usual mix, adding calcium chloride to act as a dehydrating agent and also ferric chloride which will react with the cement to result in the formation of an additional quantity of calcium chloride, and a hydroxide which acts as an initial set retarding agent.

In testimony whereof I afiix my signature.

RICHARD BUHMAN. 

